Hey, I'm not a developer/coder/programmer...
And that explains your comments quite nicely.
I don't think there is anyone here who would seriously disagree with you that the best possible scenario for the end user is dedicated UI design that is customized, when appropriate, for each target OS. But in the real world, those of us who must develop and maintain cross-OS applications with limited resources and small teams often don't have the luxury of building custom UIs for each target platform. Off-the-shelf cross-platform UI toolkits, such as Qt, are the only realistic way to support multiples OSs in these cases. It's either that, or only develop for one platform, which will usually have to be windows due to the size of the customer base. That is a far worse option, in my opinion.
So no, the "unified GUI look" that toolkits like Qt strive for across platforms is not ideal. Any serious programmer already knows that. But often times, it's the only practical way to support more than one OS, and for that reason, such toolkits are indispensable. Furthermore, those of us who don't use windows or OSX appreciate the benefits of these toolkits even more (GNU/Linux, in my case), because it means that we have far more software options than we might otherwise.